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Appendix H
Glossary
Binning: A process that may occur in the readout register and the output node (on-chip
or hardware binning) or is performed as a post-process (software binning). Binning
combines charge from rectangular groups of adjacent pixels into super pixels. When
done on-chip, this process reduces readout time and the burden on computer memory;
the drawbacks are lowered resolution and the possibility of saturation and blooming.
Software binning avoids the problem of saturation and blooming.
Blooming: The spillover of excess charge into adjacent pixels.
Bracket Pulsing: See MCP Bracket Pulsing.
Burst Mode: PTG term. Used when a short burst of very rapid gate pulses is needed to
synchronize data acquisition with a high frequency signal of interest. Occurring
during the CCD array exposure time, a burst has a maximum repetition rate of
500 kHz, generating a high voltage pulse every 2 µs. The burst can be driven from an
external trigger or from the internal oscillator.
CCD Array Dimensions and Pixel Size: Arrays that are square or nearly square are
typically used for imaging applications, while rectangular arrays are typically used in
spectroscopy applications. The smaller the pixel size, the better the resolution, but the
pixel full-well capacity smaller. Conversely, the larger the pixel size, the poorer the
resolution, and the greater the pixel full-well capacity.
CCD Array Dynamic Range: The dynamic range of a CCD is the maximum achievable
signal divided by the camera noise, where the signal strength is determined by the
full-well capacity and noise is the sum of dark and read noises. The greater the
dynamic range , the better the CCD is able to detect differences between the dimmest
and brightest intensities in an image. The readout speed affects the dynamic range of
a pixel: the faster the speed, the higher the noise, and the smaller the dynamic range.
CCD Spectral Sensitivity: Coatings applied to the CCD input window can enhance
sensitivity in the UV regions. Deep-depletion enhances sensitivity in the NIR.
Dark Charge or Dark Current: The thermally induced buildup of charge in the CCD
over time. Dark charge values vary widely from one CCD array to another and are
exponentially temperature dependent. In the case of cameras that have MPP type
arrays, the average dark charge is extremely small. However, the dark-charge
distribution is such that a significant number of pixels may exhibit a much higher
dark charge, limiting the maximum practical exposure. To minimize the collection of
dark charge, operate the camera at the lowest CCD temperature possible.
Since each CCD has its own dark charge pattern, unique to that particular device,
acquiring and saving a dark charge "background image" under conditions identical to
those used to acquire the "actual" image and then subtracting that image from the
actual image will significantly reduce dark-charge effects.
EBI: Equivalent Background Illumination. EBI comes from thermally-generated
electrons that cannot be distinguished from those generated by light photons. EBI can
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